Roller support for load handling units



May 5, 1964 G. s. ALLlN, JR

ROLLER SUPPORT FOR LOAD HANDLING UNITS Filed Jan. 10, 1962 3 Sheets-Sheet 1 a 8 f 7 Z 3. MW, 0 o 5 m 2 o u l. a W

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ROLLER SUPPORT FOR LOAD HANDLING UNITS Filed Jan. 10, 1962 3 Sheets-Sheet 2 INV EN TOR.

e0rge 61/111)? Jr.

May 5, 1964 G. s. ALLlN, JR

ROLLER SUPPORT FOR LOAD HANDLING urms 3 Sheets-Sheet 5 Filed Jan. 10, 1962 mmvrox. Qeorqe 8. /II I in, r.

e m. W5 8 United States Patent 3,131,818 ROLLER SUPPURT FOR LOAD HANDLING UNITS George S. Allin, Jr., 1337 Bond St, Green Bay, Wis. Filed Jan. 10, 1962, Ser. No. 165,448 7 Claims. (Cl. 212-69) The present invention relates to load handling units such as cranes, shovels, draglines and the like having rotatable base structures and particularly relates to units of this type in which base rotation is obtained by a roller track mechanism.

In load handling units of the type mentioned, the base structure is normally supported for rotation by rollers mounted downwardly from the base structure turntable to engage a cooperating circular track formed on the truck of the unit in surrounding relation with a vertical pintie defining the swing axis of the unit. These rollers include a number of main rollers mounted to engage the top surface of the track at suitable intervals and through which the weight of the base structure and the load handied thereby is transmitted to the truck. in addition thereto, a number of hook or equalizer rollers are mounted along the underside of the track to control tilting of the base with respect to the truck and to take-up and transmit to the truck the vertical reaction forces resulting from the overturning force of the boom. In this manner, the various forces and loads are relieved from the pintle and spread outwar 1y over the truck, enabling the unit to safely handle fairly substantial loads.

In mounting these rollers in the unit, it is of course desirable to provide a roller support of comparatively lightweight construction and which is capable of maintaining its associated rollers (or roller) in a constant, predetermined operating position with respect to the track to enable the roller-track mechanism to function properly during turning of the base structure. In the case of the hook rollers, the support structure therefor has generally consisted of a mounting shaft supported from the turntable in horizontally inwardly extending relation with the track by one or more brackets depending from the turntable and an equalizer beam pivotally supported on the inner end of the shaft and carrying a pair of the rollers directly under the track. In these supports, the shaft was ordinarily supported for rotationally adjustable movement relative to the brackets and its inner end was formed eccentrically. Thus, by adjusting the rotational position of the shaft, the beam and hence the rollers could be adjusted vertically with respect to the track to enable take-up of wear in the roller-track mechanism.

The support brackets for the shaft were of necessity, located outwardly of the outside edge of the track and, in all known previous designs, the equalizer beam was constructed such that its inner edge was also outwardly of the track edge in the assembled support. As a result, the rollers when assembled in the beam were located inwardly of the bearing formed between the beam and shaft so that the reaction centerline of the beam drawn between the rollers passed well inwardly of the centerline of the bearing. This arrangement resulted in the beam and its bearing being subjected to quite appreciable eccentric loads in service and it was therefore necessary to provide a beam of large sectional area to take these loads.

In addition, it was found that with this type of support structure the working loads on the inner end of the mounting shaft from time to time developed sunciently high moments thereon to cause significant deflection of the shaft. As the beam was merely pivoted to the shaft, any such deflection was reflected by a corresponding shifting of the beam and rollers with respect to the track. In some instances, the rollers were caused 3,131,818 Patented May 5., 1964 to become cocked on the track so as to contact the track surface along an edge of the roller only. Then, too, in some instances of deflection, the rollers, which when properly positioned are aligned axially with the swing axis of the unit to enable free rotation of the rollers on the track, were thrown out of this alignment and, as a consequence, scuffed or dragged against the track in operation. This cocking and scufiing resulted in abnormally high bearing pressures between the rollers and track and caused serious and heavy there between.

In the beam itself, parts such as the roller bushings and shafts sometimes also became cocked relatively of one another following deflection of the shaft. This not only caused heavy pressure and wear therebetween but also made it extremely difficult for the rollers to turn about their axes.

Moreover, the eccentric nature of the adjustment provided the beam and rollers led to the rollers being shifted axially with respect to the unit swing axis upon taking up wear between the rollers and track. As a consequence, it was impossible to prevent the rollers from scuffing after they had been adjusted from their initial position in the unit.

in the present invention, an equalizer beam of novel construction is provided and which enables the entire beam to be brought in and under the track whereby the working stresses thereon are substantially reduced over conventional designs.

The beam of the invention includes a transversely bored center portion receiving the inner end of the mounting shaft and a pair of angularly outwardly extending side Walls of open box construction for mounting the rollers and which are swept back or offset from the beam center portion sufiiciently for any given angularity of the side walls to move the rollers back in the beam into straddling relation with the beam center. In the assembled support then, the force reaction centerline of the beam necessarily passes through the bearing formed between the beam and the inner end of the shaft and, in the preferred form of the invention, passes directly through the center of the bearing. As a result of this construction, the normally high torsional loads experienced in beams of conventional design are substantially reduced or elimi nated altogether, thereby enabling the beam to be made considerably lighter than heretofore.

In accordance with another aspect of the invention, the equalizer beam in lieu of being pivotally connected to the shaft is connected thereto by a universal joint formed by providing the bored portion of the beam and the inner end of the shaft with complementary, partially spherical surface contours. The beam is thus free to adjust angularly as well as pivotally of the shaft whereby minor amounts of deflection in the shaft may be corrected for and the shaft adjusted rotationally as desired without causing permanent axial misalignment of the rollers with the unit swing axis. The problem of the rollers cocking and sending on the track is in this manner reduced appreciably to enable improved roller and track cooperation.

In one form of the invention, it is contemplated to support the mounting shaft from the turntable frictionally within an associated bracket to permit an infinite rotational adjustment of the shaft whereby the beam and rollers may be adjusted to the track precisely as needed for all conditions of roller and track wear. The portion of the shaft seated in the bracket is enlarged cross-sectionally sufficiently such that the frictional resistance to turning of the shaft developed in the bracket is at least equal to the maximum turning force capable of being developed on the free end of the shaft for a given shaft eccentricity and maximum design load on the shaft.

The mounting shaft may therefore be held firmly and easily in the bracket in any and all rotational positions and the desired roller and track clearance maintained at a substantially constant value.

The drawings furnished herewith illustrate the best mode presently contemplated of carrying out the invention.

In the drawings:

FIG. 1 is a side elevation of a load handling unit embodying the improved roller supports of the present invention;

PEG. 2 is an enlarged fragmentary bottom plan view of the rotating base of the unit shown in an inverted position and illustrating a typical arrangement of the rollers thereon;

FIG. 3 is an enlarged fragmentary view partly in section of the top of the truck and the base structure along the lines 3 3 of FIG. 2 illustrating the mounting in the unit of one of the after main rollers and one set of the after hook rollers;

FIG. 4 is a top elevation of an equalizer beam employed in the support structure of the hook rollers;

FIG. 5 is a side elevation of the equalizer beam shown in FIG. 4;

FIG. 6 is a cross section of the equalizer beam shown in FIGS. 4 and 5 illustrating the manner in which a roller is supported therein;

FIG. 7 is a schematic illustration of one of the support structures for the hook rollers showing the geometric relationship of the rollers to the bearing formed between the beam and shaft and to the swing axis of the unit;

1 16.8 is a schematic illustration of the structure of FIG. 3 showing the mounting shaft of the hook roller support in a deflected condition and the adjusted position of the beam thereto;

FIG. 9 is a cross section of one of the roller supports for the after hook rollers taken along the lines 9-9 of FIG. 3; and

FIG. 10 is an enlarged, fragmentary view partly in section of the base structure taken along the lines 1010 of 'FIG. 2 illustrating the mounting of the fore set of hook rollers.

Referring to the drawings, the load handling unit 1 illustrated is comprised generally of a crawler-type truck 2 and a machinery base structure 3 mounted on the truck for horizontal swing motion. Truck 2 is provided with a pair of driven, side mounted endless treads 4 (only one of which is shown) which serve to permit linear movement of the unit in operation. The center of truck 2 is formed of, an upwardly extending cylindrical portion 5 in the center of which is mounted a vertical pintle 6 defining the swing axis of the unit.

Pintle 6 extends upwardly to within a suitable pin aperture 7 provided in the turntable 8 of machinery base structure 3 and around which are provided a number of main and hook or equalizer rollers 9 and 10, respectively, cooperating with a circular track 11 formed in- 'tegrally with the top edge of portion 5 to rotatably support the base on the truck. The ends of turntable 8 overhang diametric sections of track 11 and the fore end pivotally mounts the load handling boom 12 of the unit while the after end carries one or more of the counterweights '13 to balance the base structure 3 fore and aft of the swing axis. Built up as a whole around turntable 8 is a cab structure 14 shown in outline form only. The cab structure 1 4 encloses the various operating machinery and controls of the unit, the power plant, machinery frames, hoists, etc., and which are not shown, as they form no part of the invention per se. Although not shown, the truck drive transmission and the gear mechanism for compelling rotation of the base and which cooperates with a ring gear 15 formed around the inner periphery of track 11 (see FIG. 3) are mounted downwardly to the truck from the base as is known in the art, the

turntable 8 being provided with a number of openings 16 for this purpose.

In the illustrated embodiment of the invention, main rollers '9 are mounted separate and distinct from hook rollers '10 and, as shown in FIG. 2, the fore end of turntable 8 is provided with two main rollers located one each approximately 30 to either side of the fore and aft centerline of unit 1 while the after portion is also provided with two main rollers disposed similarly to the aforesaid centerline. It will be understood that the particular num her and disposition of main rollers 9, as well as that of hook rollers 10 to be described, is solely for the purpose of illustration and is in no way to be construed as a limitation or requirement of the, present invention. Main rollers 9 transmit the weight of machinery base structure 3 and the load handled thereby to track 2 through the upper surface 17 of track 11 and are housed or cradled directly within turntable 8 in the fore and aft pairs of downwardly opening, recesses 18 case integrally. Recesses 18 are located in a turntable 8 directly above corresponding sections of track surface 17 and are disposed angularly with respect to the fore-aft centerline of the unit so as to maintain in registry with track 11 in all swing positions of base structure 3. The rollers 9 are of annular construction and are supportedly held for rotation in recesses 18 in downwardly engaging relation with track surface 17 by a roller shaft 19 extended between opposed wall portions of the recesses in axial alignment with the unit swing axis. Shafts 19 are fixed against rotation by any suitable means such as the snap rings 29. A bushing 21 is inserted between each of the shafts 19 and the corresponding roller 9 and a thrust washer 22 is provided between rollers 9 and the opposite walls of recess 18 as shown to fix the rollers axially of shafts 19.

Roller shafts 19 are thus supported rigidly in the turntable proper in the manner of a fixed ended beam and are capable of withstanding high working loads with minimum deflection, thereby minimizing cocking and/or scufling of rollers 9 on track surface 17.

The book rollers 10, as shown, are mounted in-tandem or pairs and, in the illustrated construction, two sets of rollers 10 are provided on the after portion of turntable 8, one each under each of the after main rollers 9, while a third set is provided at the fore end of turntable 8 directly on the fore and aft axis of the unit. Hook rollers 10 are adapted to engage the lower surface 23 of track 11 to limit tipping of base structure 3 with respect to truck 2 to the clearance afforded between the rollers and track.

The roller supports for the two after sets of hook rollers 10 are indicated by the reference numeral 24 and, as they are of identical construction, only one such support need be described herein. Essentially, roller supports 24 comprise a mounting pin or shaft 25 supported under turntable 8 in horizontally inwardly extending position rela. tive to track 11 by the outer and inner frictional brackets 26 and 27, respectively, and an equalizer beam 28 carrying rollers 16 and supported on the inner end 29 of shaft 25 which extends to a point directly below track surface 23 as shown. Outer bracket 26 is formed of the separate clamp members 30 and 31 having the semi-cylindrical gripping surfaces 3-2 on their corresponding ends. Member 30 is secured to turntable 8 aft of the corresponding recess 18 as by welding and members 30 and 31 removably secured together in frictional engagement with the outer end portion 33 of shaft 25 by a number of fastening bolts 34. In order to locate shaft 25 correctly with respect to track 11, shaft end portion 33 is provided with a pair of spaced, circumferentially extending grooves 35 I which seat bolts 34 to provide an indexing means for the shaft in the brackets 26 and 27.

Inner bracket 27 is formed integrally with turntable 8 closely adjacent the outside edge of track 11 and in general alignment with bracket 26 and with the unit swing axis to enable shaft 25 to be aligned axially with the swing axis. Shaft 25 is supported in bracket 27 within a circular opening 35 provided therein and which is machined to within a relatively close allowance of the corresponding portion 37 of shaft to provide an additive frictional force to that of bracket 26 opposing turning of the shaft 25. In this manner, shaft 25 is rigidly supported from turntable 8 and, by reason of bracket 27 being in close proximity to track 11, there is a minimum moment arm available at shaft end 29 for loads imposed thereon.

In order to take-up wear in the roller-track mechanism and maintain a predetermined clearance between rollers 10 and track surface 23, shaft end 29 is formed eccentrically or off-center with respect to the longitudinal axis of the shaft. Thus, by varying the rotatinoal position of shaft 25 relative to brackets 26 and 27, beam 28 and the rollers 19 supported thereby will be adjusted vertically with respect to track surface 23. To facilitate his adjustment, fixed end portion 33 of shaft 25 is constructed to project outwardly of bracket 26 when assembled therein and the projecting portion provided with a diametrically extending opening 38 for applying a rod (not shown) to the shaft to turn the same.

In the present construction, it will be noted that an infinite rotational adjustment of shaft 25 is possible by reason of the design of brackets 26 and 27 This is desirable in that it permits rollers It to be adjusted to track surface 23 the precise amount required under all conditions of track and roller wear. In order to prevent any possible turning of shaft 25 in brackets 26 and 27 during use due to turning forces developed on the shaft by reason of its eccentric construction, the frictional resistance t turning developed by brackets 26 and 27 must at all times equal or exceed these turning forces. In the present invention, bracket 27 is utilized to provide the principal frictional force holding shaft 25 stationary. To this end, previously referred to shaft portion 37 and which seats in bracket opening 36 is enlarged diametrically an amount which is a predetermined function of the degree of eccentricity of shaft end 2? and the loads on the latter and on bracket 27. In particular, let X represent the diameter of shaft portion 37, Y the maximum eccentricity of shaft end 255 to the shaft proper, L the maximum theoretical design load on shaft end 29, R the corresponding reaction force at bracket 27, and letting ,u represent the coefficient of friction of dry steel on dry steel, Lie diameter of shaft portion 37 is designed in accordance with the following relationship It will be seen then that bracket 27 in and of itself is capable of preventing turning of shaft 25 in brackets 26 and 27 in any rotational position of the shaft and that the frictional force developed by bracket 26 against turning of the shaft is merely additive to that of bracket 27. This additive frictional resistance may be desirable where it is preferred to grease the bearing of shaft 25 in bracket 27. However, even with a lubricated bearing, only a relatively small turning moment will be transmitted to bracket 26 and then only when shaft end 2? is positioned to provide maximum eccentricity for the loads thereon due to the increased diameter of shaft portion 37.

In the present support, beam 2-3 and rollers 10 may be adjusted relative to track surface 23 exactly as needed to maintain a predetermined clearance between the rollers and track and thereafter firmly held in such position until such time as further adjustment is desired.

Turning now to the construction of beam 28, the present invention provides a design which enables the beam to be supported in and under track surface 23 in its entirety thereby reducing the overall workinug stresses on the beam and enabling the same to be of lightweight construction. As particularly shown in FIGS. 4 to 6 of the drawings, beam is an integral casting including a hub portion 39 having a bore provided therein transversely of the beam to receive shaft end 29 and a of oppositely,

outwardly extending side walls 41 formed symmetrically about the axis of bore 40. Side Walls 41 have a generally open box construciton and include the opposed apertured wall portions 42 forming bearing supports for a roller shaft 43 fixedly held by a set screw 44. Rollers 10 have an annular form and are journalled in side walls 41 on shaft 43 by a bushing 45 assembled between shafts 43 and rollers 19 and press fitted to the latter. The roller and bushing assembly is fixed axially of shaft 43 by a thrust washer 46 disposed on shaft 43 between a wall portion 42 and the corresponding end of the roller and bushing assembly as shown. In order to lubricate the bearing surfaces of bushing 45 and shaft 43, the shaft is provided with a series of internal, interconnecting passageways 47 which register with a passageway 48 in one of wall portions 42 receiving a grease fitting 49.

In these roller-track mechanisms, rollers 10 are required to be positioned under the track in axial alignment with the swing axis of the unit to enable free turn ing of the rollers when on the track. For this purpose, it becomes necessary to form. side walls 41 angularly with respect to the longitudinal axis of the beam. To provide for the required angularity in walls 41 while at the same time permitting the entire beam to be brought in and under track surface 23, in the present invention side walls 41 are set back or offset from hub 39 and relative to the longitudinal beam axis an amount such that with beam 28 assembled on shaft end 29, rollers 1% lie directly under track surface 23 and in straddling relation with the bearing formed between shaft end 29 and bore 49. In the preferred form of the inveniton, the offset of side walls 41 is calculated so that for any given side wall angularity, rollers it) are disposed in beam 28 with their mass centers in a common vertical plane with one another and With the centerline of the bearing of the beam on shaft end 29.

Jith this arrangement, the force reaction centerline of beam 23 necessarily passes through the centerline of the bearing of beam 28 on shaft end 29 with the result that beam loads at all times stress the beam and its bearing in bending alone. As compared to former designs where beam loads were applied eccentrically with respect to the beam and the bearing thereof due to the reaction centerline of the beam bieng well inwardly of the bearing, the present construction enables a substantially lighter construction for the beam while at the same time increasing the overall rated load which the unit may safely handle. For example, in an actual case, it was found that with the present construction, an equalizer beam which formerly weighed 170 pounds could be reduced to a weight of approximately 59 pounds and at the same time where the former beam was designed for use in a 66 ton unit, the new beam was satisfactory for use in a ton unit.

The above described arrangement of rollers it) in the beam 2% may be best understood by referring to FIG. 7 of the drawings which represents a schematic illustration of support 24. In this figure, the mass centers of rollers it) are indicated at 59, the center of the bearing between beam 23 and shaft end 29 at 51, and the force reaction centerline of beam 2% by the line 52. The two lines 53 and the single line 54 in this figure are drawn axially through rollers lit and the principal axis of shaft 25 and respectively, and extended to the swing axis of unit 1 indicated at 55.

Regarding the mounting of beam 28 to shaft end 29, it is desirable to maintain beam 28 and rollers it? supported thereby in a substantially constant operating position with respect to track surface 23 irrespective to shaft 25 being deflected and irrespective of the rotational position of the shaft in brackets 25 and 27 at any particular instant. For this purpose, shaft end 29 is machined with a partially spherical, ball-like surface contour as shown. The wall of bore 46 is machined in conformity with shaft end 29 and to within a predetermined nominal allowance thereof whereby the beam and shaft when assembled form'a balland-socket joint 56 to retain beam 29 on shaft 25 for limited universally adjustable movement thereof. The center of ball joint 56 lies on the force reaction centerline of beam 28 due to the previously described design of the beam with the result that beam 28 is at all times urged to move relatively of shaft 25 about the center of ball joint 56. The beam is thereby precluded from binding on shaft end 29 in operation.

As opposed to the simple pivot connection normally employed between the beam and its shaft, the present construction permits beam 28 to adjust its relative position on shaft 25 as required to compensate for limited amounts of deflection in the shaft and/or rotational ad justments of the shaft relative to brackets 26 and 27 as in taking up wear in the roller-track mechanism. Rollers are thus more effectively able to maintain a position of flush bearing engagement with track surface 23 and one of axial alignment with the unit swing axis than in prior designs. Effects such as scufiing and cocking of the rollers on the track are thereby minimized to provide improved, all around functioning of the rollertrack mechanism.

By way of illustrating the functioning of joint 56, a schematic illustration of a support 24 embodying the present invention is provided in FIG. 3 of the drawings with the shaft 25 of the support being shown in a deflected condition. Ordinarily, such deflection would result in cocking of rollers 10 on track surface 23 but owing to the provision of joint 56, in the present construction the beam is able to move angularly of shaft 25 sufficiently to permit full surface contact of rollers 10 on track surface 23 as shown.

The roller support for the fore pair of hook rollers,

V and which is indicated at 57 in the drawings, has the same basic construction as previously described for support 24. The mounting shaft 58 is in this instance made considerably shorter in length than shafts 25 due to the smaller overhang at the front of unit 1 and is supported by a single bracket 59 formed integrally with turntable 8. Bracket 59 is provided with an opening 60 in its lower end to receive shaft 58 and which is machined to within a nominal allowance of the shaft to frictionally grip the latter. The outer end of shaft 58 is modified by the provision thereon of a radially enlarged head 61 having the circumferentially extending serrations 62. Head 61 abuts bracket 59 upon shaft 58 being inserted fully in the bracket to limit inward movement of shaft 58 while a recessed keeper plate 63, removably secured to the outer ,face of bracket 59 over shaft head 61 by a bolt 64, is

provided to restrain shaft 58 from moving outwardly of the bracket. The recessed portion of plate 63 is provided with the circumferentially extending serrations 65 interlocking with serrations 62 on shaft head 61 to provide an additive force with bracket 59 opposing rotation of shaft 58 in the bracket.

As in the case of shafts 25, shaft 58 is formed eccentrically on its free end 66 and mounts an equalizer beam 67 whereby the beam and its rollers 10 may be adjusted vertically with respect to track surface .23 by adjusting shaft 58 rotationally in bracket 59 within the limits permitted by the serrations 62 and 65.

The turning moment developed on shaft 58 due to the eccentricity of free end 66 is taken up primarily by bracket 59 by providing the shaft portion 68 seated therein with a fairly appreciable diameter.

Keeper plate 63 provides an additive opposing force to turning of shaft 58 and, if desired, allows the bearing of shaft 58 in bracket 59 to be lubricated without risk of Lhe shaft turning when in operation.

The construction of beam 67 is identical in all respects 'to that described for beam 23 as is the mounting of the beam to the inner end of theshaft and the structure for supporting the rollers in the beam. Accordingly, a detailed description and showing thereof need not be provided herein. t

The" improved roller supports of the invention are highly advantageous in that they not only permit substantial reductions in the weight and cost of the equalizer beam but also provide means for correcting minor misalignments between the rollers and track. While described in connection with the hook rollers only, the proposed supports may be utilized equally well with the main rollers where such is desired or where alternative supports are not feasible.

Various modes of carrying out the invention are contemplated as being within the scope of the following claims particularly pointing out and distinctly claiming the subject matter which is regarded as the invention.

I claim:

1. In a roller support structure of a load handling unit having a rotatable base structure and a truck for supporting said base on a horizontal track formed integrally with said truck, said support structure including a fixed ended mounting shaft secured for rotationally adjustable movement on the underside of the base and having an eccentrically formed end portion supported freely and in vertically spaced relation with said track and an equalizer beam supported on the eccentric end portion of the shaft for vertically adjustable movement with respect to said track and carrying a pair of rollers in predetermined vertical relation with said track, the improvement comprising providing a universal joint between said beam and the eccentric end portion of said shaft to permit limited universally pivoting of said beam relatively of said shaft thereby permitting said beam and rollers to maintain a substantially predetermined, constant operating position with respect to said track irrespective of limited deflection and rotational adjustment of the shaft.

2. The construction of claim 1 wherein said rollers are mounted in said beam in straddling relation with said joint and with the mass centers of said rollers in a vertical plane with the mass center of said joint so that beam reaction forces are at all times applied through the center or" said joint to enable said beam to pivot freely on said shaft in all planes within the limits of said universal joint.

3. In combination in a rotatable base structure supported by rollers upon a circular track member having upper and lower track surfaces and a plurality of book rollers carried by brackets depending from said base and disposed to engage the underside of said track to stabilize said base thereon, mounting means for said hook rollers comprising an equalizer beam for each pair of rollers and disposing the same with their axes generally normal to the rotational center axis of said base structure, a trunnion shaft centrally supporting said equalizer beam intermediate the corresponding pair of rollers and carried by a corresponding bracket depending from said base, the inner end of each said shaft constituting a bearing support for the corresponding equalizer beam and being constructed to provide limited universal pivotalfmovement of the beam relative to the shaft to thereby provide free adjustment of the hook rollers to the track.

4. In combination in a rotatable base structure supported by rollers upon a circular track member having upper and lower track surfaces and a plurality of hook rollers carried by brackets depending from said base and disposed to engage the underside of said track to stabilize said base thereon, mounting means for said hook rollers comprising an equalizer beam for each pair of rollers and disposing the same with their axes generally normal to the rotational center axis of said' base structure, a trunnion shaft centrally supporting said equalizer beam intermediate the corresponding pair of rollers and carried by a corresponding bracket depending from said base, the inner end of each said shaft constituting a bearing support for the corresponding equalizer beam with the center of the bearing disposed substantially in the vertical plane containing the center points ofcontact between the corresponding pair of hook rollers and the track.

5. The construction. of claim 4 in Which the inner end of each said shaft is disposed eccentrically relative to the shaft and the shaft is mounted for rotational adjustment in its bracket to provide for adjustment of the hook rollers vertically of said track.

6. The construction of claim 4 in which said bearing support is generally convex to provide limited universal pivotal movement of the beam relative thereto and thereby enable said hook rollers to freely adjust to the track.

7. The construction of claim 6 in which the inner end 10 of each said shaft is disposed eccentrically relative to the shaft and the shaft is mounted for rotational adjustment in its bracket to provide for adjustment of the hook rollers vertically of said track.

References Cited in the file of this patent UNITED STATES PATENTS McGifiert et a1 Feb. 16, 1937 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,131,818 May 5, 1964 George S. Allin, Jr,

It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

In the grant, lines 1 to 3, for "George S, Allin, Jr, of Green Bay, Wisconsin," read George S. Allin, Jr of Green Bay, Wisconsin, assignor to Northwest Engineering Corporation, of Green Bay, Wisconsin, a corporation of Wisconsin, line 12, for "George S. Allin, Jr, his heirs" read Northwest Engineering Corporation, its successors in the heading to the printed specification, line 3, for "George S. Allin, Jr. 1337 Bond St. Green Bay, Wis." read George S. Allin, Jr, Green Bay, Wis. assignor to Northwest Engineering Corporation, Green Bay, Wis. a corporation of Wisconsin column 2, line 10, after "heavy" insert wear column 4, line 19, for "case" read cast column 5, line 13, for rotatinoal" read rotational line 70, for "workinug" read working column 6, line 413, for "bieng" read being line 67, for "to", second occurrence, read Signed and sealed this 15th day of September 1964,

(SEAL) Attest:

ERNEST W. SWIDER EDWARD J, BRENNER Attesting Officer Commissioner of Patents 

1. IN A ROLLER SUPPORT STRUCTURE OF A LOAD HANDLING UNIT HAVING A ROTATABLE BASE STRUCTURE AND A TRUCK FOR SUPPORTING SAID BASE ON A HORIZONTAL TRACK FORMED INTEGRALLY WITH SAID TRUCK, SAID SUPPORT STRUCTURE INCLUDING A FIXED ENDED MOUNTING SHAFT SECURED FOR ROTATIONALLY ADJUSTABLE MOVEMENT ON THE UNDERSIDE OF THE BASE AND HAVING AN ECCENTRICALLY FORMED END PORTION SUPPORTED FREELY AND IN VERTICALLY SPACED RELATION WITH SAID TRACK AND AN EQUALIZER BEAM SUPPORTED ON THE ECCENTRIC END PORTION OF THE SHAFT FOR VERTICALLY ADJUSTABLE MOVEMENT WITH RESPECT TO SAID TRACK AND CARRYING A PAIR OF ROLLERS IN PERDETERMINED VERTICAL RELATION WITH SAID TRACK, THE IMPROVEMENT COMPRISING PROVIDING A UNIVERSAL JOINT BETWEEN SAID BEAM AND THE ECCENTRIC END PORTION OF SAID SHAFT TO PERMIT LIMITED UNIVERSALLY PIVOTING OF SAID BEAM RELATIVELY OF SAID SHAFT THEREBY PERMITTING SAID BEAM AND ROLLERS TO MAINTAIN A SUBSTANTIALLY PREDETERMINED, CONSTANT OPERATING POSITION WITH RESPECT TO SAID TRACK IRRESPECTIVE OF LIMITED DEFLECTION AND ROTATIONAL ADJUSTMENT OF THE SHAFT. 